invention is directed to a surgical procedure for relieving nerve entrapment such as Carpal Tunnel Syndrome by increasing the spatial diameter of the tunnel enclosing the nerve.
Carpal Tunnel Syndrome is a common painful condition of the hand characterized by a decrease in median nerve sensibility with paresthesias of the fingers. It is the most common nerve entrapment syndrome of the upper extremity and results from compression of the median nerve in the carpal tunnel and provides nocturnal pain, clumsiness, and weakness of grasp or pinch.
The carpal canal is the area in the wrist and palm of the hand formed by the U-shaped cluster of bones of the carpus that forms the rigid hard floor and the two sides of the tunnel. Within the confines of this space are the median nerve, and the extrinsic flexor tendons of the thumb and fingers with their surrounding synovial membranes of the radial and ulna brusae. The roof of the tunnel is formed by the transverse carpal ligament on the palmar surface of the carpal bones. The ligament is attached medially to the pisiform and the hamulus of the hamate and laterally to the tuberosity of the scaphoid and the medial part of the palmar surface and ridge of the trapezium. The proximal border of the ligament is partially merged to the distal border of the palmar carpal ligament, but this is a more superficial structure and is separated from it by the ulnar artery and nerve. The transverse carpal ligament is attached to the palmar aponeurosis, which lies superficial, and contributes crossed oblique fibers to the deep surface of the aponeurosis. (Goss, Charles Mayo Ed.; Gray's Anatomy; Twenty-ninth American Edition, p 473.)
Any condition that diminishes the size of the carpal tunnel can precipatate the Carpal Tunnel Syndrome (Milford, Lee., Campbell's Operative Orthopaedics., 7th Ed: 459). Repetitive wrist and hand motions can cause thickening and hypertrophy of the transverse carpal ligament. Also, proliferation of synovium from normal wear and tear of daily activities can cause compression of the median nerve within the closed confines of the carpal tunnel. A previous fracture or dislocation of the wrist may cause bone to protrude with narrowing of the tunnel. Furthermore, systemic conditions such as pregnancy, obesity, diabetes, mellitus, thyroid dysfunction, or chronic renal failure can initiate the syndrome. Generally, the syndrome occurs most often in patients between the ages of 30 and 60 years and is five times more frequent in women than in men Milford, Lee., Campbell's Operative Orthopaedics., 7th Ed: 459). Clinical diagnosis is established by medical history, physical examination including the Phalen wrist flexion test Phelen, G. S.: The carpal tunnel syndrome: 17 years experience. J. Bone Joint Surgery., 48A:211-228, 1966) and Tinel's sign as well as the median nerve oompression test. Thenar atrophy to some degree may be evident with prolonged compression of the median nerve.
Carpal tunnel pressure measurements have been studied in symptomatic patients and such studies showed a marked increase in the mean pressure of the carpal tunnel from 32 mm with the wrist in neutral position to 99 mm with 90 degrees of flexion and 110 mm with the wrist in extension. Normal control measurements were 2.5 mm in neutral position, 31 mm in flexion, and 30 mm with wrist extension ( Gelberman, R. H., Hergenroeder, P. T., Hargens, A. R., Lundborg, G. N., and Akerson, W. H.: The carpal tunnel syndrome: as study of carpal tunnel pressures, J. Bone Joint Surg. 65-A:380, 1981).
Electromyelographic studies in classical carpal tunnel syndrome show a distal wrist latency in conduction velocity. Prolongation of the distal sensory latency above 3.5 Msec has been found to be present in 85 to 95 per cent of surgically confirmed cases (Heckler, F. R., Jabaley, M. D.: Evolving concepts of median nerve decompression in the carpal tunnel: Hand Clinics 2(4):723-726, 1986). Irreversible muscle damage is indicated by denervation potentials.
Historically, carpal tunnel syndrome has been treated nonsurgically by splinting of the affected hand and wrist, oral antiinflammatory medioation, and local steroid injection. If nonsurgical methods are unsuccessful surgical intervention is indicated.
Open surgical decompression of the carpal tunnel by division of the transverse carpal ligament was first described in 1930 by Learmonth. Open procedures generally entail a curved longitudinal incision ulnar to and parallel to the thenar crease. Taleisnik described an incision along the ulnar border of the ring finger axis (Taleisnik, J.: The palmar cutaneous branch of the median nerve and the approach to the carpal tunnel: An anatomical study; Bond Joint Surg, 55A: 1212, 1973). This incision may extended proximally to the wrist flexor crease. Angling the incision towards the ulnar aspect of the wrist helps to avoid cutting the palmar sensory cutaneous branch of the median nerve. This nerve is located in the interval between the palmaris longus and the flexor carpi radialis tendons. After division of the skin and subcutaneous tissue, the transverse carpal ligament is identified and divided along its ulnar border to avoid and to prevent injury to the median nerve or its recurrent branch.
Open surgical decompression of the median nerve is not without risks and complications (Kuschner, Stuart H, Brien, William W, et al.; Complications associated with carpal tunnel release; Orthopedic Review: April 1991; Vol XX; Number 4:346-351). Long term analysis of patients having surgical treatment for carpal tunnel syndrome have shown a failure rate as high as 19% (Kulick, Michael, I., D.D.S., M.D., et al.; Long-term analysis of patients having surgical treatment of carpal tunnel syndrome,; Jour of Hand Surg; 11A (1):59-66. 1986). A study noted in The Journal of the American Medical Association in April, 1991 found "the initial relief of open carpal tunnel surgery to be shadowed by significant scar pain and weakness in almost a third of subjects after 2 years." (Nancollas, Michael P.; Symptoms may return after carpal tunnel surgery; JAMA,; Vol 265, No 15, p 1922, April 17, 1991). Thirty percent of all patients in the study were rated with poor or fair result at an average of 5.5 years follow-up "57% of the patients in the study complained of return of some preoperative symptoms, most commonly pain, beginning an average of 2 years after surgery." (Nancollas, Michael P.; Symptoms may return after carpal tunnel surgery; JAMA,; Vol 265, No 15, p 1922, Apr. 17, 1991.) Complications include continued pain and or numbness, hypersensitive scar, loss of grip strength, joint stiffness, adherence of flexor tendons, neuroma, injury to the median nerve or its' motor branch or digital nerve injury, damage to the palmar cutaneous nerve, vascular injury, palmar hematoma, infection, and possible reflex sympathetic dystrophy.
A retrospective analysis of 40 cases of reoperation for carpal tunnel syndrome found adhesions and fibrosis around the median nerve in the carpal canal in 36 cases. (Wadstroem, J., Nigst, H.,; Reoperation for carpal tunnel syndrome: a retrospective analysis of 40 cases; Ann. Chir. Main; 5:54-58, 986.)
Hand weakness with loss of grip strength can also be a problem. Carpal tunnel release produces an average widening of the transverse carpal arch of 2.7 mm. There is a direct relationship between widening of the carpal canal and decreased grip strength. The average decrease in grip strength is 12%. (Gartsman, Gary, M., Kovach, John, C., et al.; Carpal arch alteration after carpal tunnel release; J. Hand Surg. (AM.) 11-A:372-374, May, 1986.) Computerized tomographic (CT) studies of the carpal tunnel after transsection of the transverse carpal igament have shown that if the flexor retinaculum is not intact, the flexor tendons will bowstring palmarly while the wrist and fingers are flexed together, causing weakness of grip. Some authors have recommended the use of a firm postoperative compression dressing immobilizing the wrist in slight dorsal extension for 3 weeks to prevent prolapse of the flexor tendons. (Jessurun, W, Hillen, B, et al.; Carpal tunnel release: Postoperative care: Handchirurgie 20:39-40, January, 1988.)
Because of the concern over widening of the carpal arch with subsequent decrease in grip strength, following standard carpal tunnel re1ease, Jakab and associates devised a technique employing reconstruction of the transverse carpal ligament. (Jakab, Emery, Ganos, Doreen, et al.; Carpal tunnel release: Postoperative care: Handchirurgie 20:39-40, January, 1988.) These authors stated that by reconstructing the transverse carpal ligament, the transverse carpal arch was stabilized affording protection to the median nerve and preventing potential bowstringing of the flexor tendons. By repairing the transverse carpal ligament the normal relationship of the carpal canal and its contents was restored and maintained.
Pre and post operative CT scanning of the wrist in carpal tunnel syndrome has been performed and has shown that postoperative decompression results in the regeneration of a much more flexible ligament, which allows the contents of the tunnel, to expand anteriorly. The divided transverse carpal ligament heals in a stretched or arched position allowing more room for the median nerve and flexor tendons. (Chaise, F., Roger, B.,; Pre-and post-operative CT scanning of the wrist in carpal tunnel syndrome; Rev Chir. Orthop.; 72:297-302' 1986.)
In recent years endoscopic techniques have been utilized to incise and divide the transverse carpal ligament, (Agee, John, M., et al.; Results of a study on the effectiveness of endoscopic release of the carpal tunnel; American Society for Surgery of the Hand, 45th annual meeting; Okutsu I, Ninomiya S, et al.; Endoscopic management of carpal tunnel syndrome; Arthroscopy: 7(1):11-18, 1989; Okutsu I, Ninomiya S, et al.; Measurement of pressure in the carpal canal before and after endoscopic management of carpal tunnel syndrome: J. Bone Joint Surg: 71A (5):679-683, 1989;Chow, J. D. : Endoscopic release of the carpal Iigament: A new technique for carpal tunnel syndrome: Arthroscopy: 5(1): 19-24, 1989.) Attempts have been made to decrease the size of the surgical incision with the benefit of decreasing postoperative morbidity because hand strength returns more quickIy and the hand is less tender. (Quote: John M. Agee, M.D.; Endoscopic carpal tunnel release gentler than open; Orthopedics Today: February, 1991; p.24) Refinements of endoscopic release of the carpal ligament have been evolving but complications with this procedure have been reported The complications include neuropraxia of the median and or ulnar nerve, digital nerve laceration, laceration of palmar vessels, laceration of flexor tendons, neuropraxia or laceration of the palmar cutaneous branch of the median nerve, palmar hematoma, adhesions of tendons, perineural fibrosis, bowstringing of flexor tendons with loss of grip strength, incomplete transaction of the carpal ligament with recurrence of symptoms and hypertrophic scar. (Resnick, Charles T., Miller, Brent, W.: Endoscopic carpal tunnel release using the subligamentous two-portal technique; Contemporary Orthopaedics, Vol: 22 (3), March, 1991:269-277.) A dual incision technique has been developed (Chow, James, C., Y.; Endoscopic release of the carpal ligament: A new technique for carpaI tunnel syndrome; Arthroscopy: 7(1): 19-24, 1989) with attempt to further increase the safety and efficacy of the endoscopic procedure but the potential complications of surgically transsecting the transverse carpal ligaments remain evident. A recent study was reported where endoscopic carpal tunnel release was practiced on 13 fresh-frozen cadaver hands by surgeons who had "extensive" clinical endoscopic carpal tunnel surgery experience at three Boston, Massachusetts teaching hospitals. Complete release of the transverse carpal ligament was achieved in only five of the cadaver hands. Endoscopically, the incomplete release of the ligment occurred distally, "where concern about the superficiaI palmar arch may have caused hesitation." It was found that the fat pad between the transacted edges of the transverse carpal ligament obscures the view through the endoscope and neurovascular structures may not be directly observed. (Schwartz, Jr., J. Tphomas; Symptoms may return after carpal tunnel surgery; JAMA,; Vol 265, No 15, p. 1925, Apr. 17, 1991) It was concluded that, "the recurrence rate in patients undergoing endoscopic carpal tunnel release must be scrutinized long term in light of the high incidence of incomplete sectioning of the ligament and the narrow margin of safety". (Schwartz, Jr., J. Thomas; Symptoms may return after carpal tunnel surgery; JAMA; Vol 265, No 15, p. 1925, Apr. 17, 1991).
Various patents disclose devices for inserting or placing catheters within chosen parts of the human body. U.S. Pat. No. 4,655,214 discIoses a soft inflatable introducer having a closed rounded distal tip sheath. After insertion and placement of the introducer with sheath adjacent to distal end of a catheter, the sheath is inflated and approximal end of the sheath is sealed to maintained it in expanded inflatable condition where catheter is being intubated. After the catheter has been intubated, a clamp of the sheath is opened to deflate the sheath into the introducer withdrawn. U.S. Pat. No. 4,645,491 discloses a catheter placement apparatus used in inserting a catheter to a preferred depth. The device is constructed of a surgical needle provided with a longitudinal window to which a catheter inserted in the needle can be viewed. The catheter has a colored patch of the same length as the window in the series of spaced visually distinct markings allowing the position of the catheter to be accurately located by lining the colored patch with the window and inserting the catheter until at least one mark appears in the window, to determine, the distance of the mark from the surface of the skin. U.S. Pat. No. 3,537,452 discloses a needle guard and beveled cutter for use with intravenous catheterization units. The device has a tubular body with a flat base and a longitudinally slotted top. The diameter of the tube is greater than the diameter of the needIe contained therein. U.S. Pat. No. 3,592,193 discloses a removable needle guide to be used with a flexible catheter tube in withdrawing or introducing fluids relative to a body. The needle guide has winged handles associated therewith which provides controlled insertion and removing from the body with subsequent attachment from a flexible catheter tube. U S. Pat. No. 5,011,478 discloses an introducer set including a sheath and dilator formed with a smooth external shape. The distal end of the sheath is embedded in the dilator and formed in angle oblique to the longitudinal access of the introducer set. U.S. Pat. No. 3,559,643 discloses a catheter placement unit for insertion of a catheter into a body lumen through an incised opening in the lumen wall. The unit includes a longitudinally slit sheath having a catheter therein and an advancer connected to one end of the catheter, initially and axial alignment with the sheath to close the end of the sheath.